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[johnmowcop]

I know this may invoke ridicule, but it won't be the first time I have left that door open.

Has anyone lowered the compression ration to make the engine even more tractable, if so how did they do it and what was the outcome.

JohnT

[Para Bellum]

My 110s were so responsive, it was a problem in slow-speed maneuvering.  For me, tractable meant less jerky at small throttle openings.  With a tuner (TTS in my case), it was easy:  using throttle-blade control in the tuner, I adjusted the system so the throttle blade did not open as much as the throttle called for.  Example: at 2% throttle, the blade was only at 1% open; at 4% throttle, only 2% open; and so on until about 10% throttle, where it became 10% = 10%.  That took care of the problem, without losing the benefits of a higher-powered engine...just whack the throttle above the 10% level and enjoy.  It also was a lot easier than detuning the engine.

[grc]

You probably should explain what you mean by tractability John.  If you are in fact talking about low speed smoothness of operation, Para Bellum gave you a much better idea than detuning the engine.  And just lowering the compression ratio would not have your desired effect anyway.  It also makes a difference if you have the tune adjusted in the low speed range (fuel and timing), which can smooth the engine response significantly compared to the stock Harley calibrations.  These kinds of changes won't hurt performance at higher engine speeds, a compression change will.

Jerry

[johnmowcop]

I know this may invoke ridicule, but it won't be the first time I have left that door open.

Has anyone lowered the compression ration to make the engine even more tractable, if so how did they do it and what was the outcome.

JohnT

Para Bellum and Jerry,

Thank you for taking the time to respond. You may have "hit the nail on the  head" with your thoughts. One of my previous posts was about a jerky throttle response when on rough roads, which are prevalent in my area of UK. I am after a smoother power take up, particularly in traffic, as Para Bellum states. The power feed/take up is too harsh for slow/steady riding.
I will ask the local dynojet tuner, been considering a Power Vision remap anyway, I will see if it can be part of the setup for that to soften the first 10% of the throttle as stated.

JohnT

[timo482]

i lowered the gearing on my 07 w sidecar - best thing I've done. tractability? yes this fixed that, no jerking, just smooth.

also installed the new compensator - i needed one part of the original - no longer available had to do the upgrade that includes the new alternator rotor.

lots of work, not a lot of money. its 30 - 70 now and soooo much better.

i also changed the lifters - had one spot of hard surface that had flaked off of one lifter 1mm x 2mm - nothing i could see on the cam lobe so i installed the new lifters and it runs perfect.

[Dan_Lockwood]

My '09 has always been a slug off the line due to the stepped up drive ratio.  I would have to slip the clutch a lot riding two up and when going slow, the bike was too fast without pulling in the clutch a bit here and there.

But once moving it wasn't too bad.

I did change out the 32t trans drive sprocket with a 30t.  I decided to retain the stock belt so I was forced to do the swingarm adjustment slot modification.  Having the necessary tools and welder in my home garage and a table lift, made this a nice weekend job.  The hardest part was removing the retaining nut on the trans sprocket.  Had to make up a deep socket to do this.  Also bent a 3/4" breaker bar with a 5' pipe on the end just to break loose the nut.  Also heated the nut and finally the red Loctite broke loose.

After the install of the 30t sprocket, my bike, one up or two up, became so much more ride-able at lower speeds.  It was a HUGE improvement for the investment.  I gained about 300 rpms in each gear versus the old mph speeds/rpms.  But 6th gear is now very usable, even down in the 50 mph range.  And taking off in 1st is not an issue anymore, no need for as much clutch feathering.

I agree tuning with the TTS is a good option.  I have the TTS on mine, but have not played with the adjustments as mentioned above.  But over all of my mods, the 30t conversion was the most bang for the buck and VERY noticeable in use.

Good luck and let us know how it works out for you.